1. Field of the Invention
The present invention relates to electrical sensors of the type useful for controlling electrical flow through a circuit. The present invention specifically involves the use of a tactile feedback dome-cap in conjunction with pressure-sensitive variable-conductance material to provide momentary-On pressure dependent variable electrical output. The tactile feedback is user discernable for indicating actuation and de-actuation of the sensor. Novel structural embodiments and methods of manufacturing are disclosed.
2. Description of the Related Prior Art
There are many prior art types of switches (sensors) and switch packages. While used widely in many fields, switches and switch packages are used in game controllers for use in controlling imagery, and in computer keyboards, other computer peripherals, and in many other host devices not related to computers.
A very common prior art switch is comprised of: a housing typically of non-conductive plastics; a first and a second conductive element fixed to the housing and in-part within the housing and in-part exposed external of the housing; a conductive dome-cap typically made of metal having a degree of resiliency and positioned within a recess of the housing and between a depressible actuator and the two conductive elements. The actuator is retained to the housing via a flange of the actuator positioned beneath a housing plate with a portion of the actuator extending through a hole in the housing plate to be exposed external of the housing and thus accessible for depression by a mechanical member or a human finger or thumb. Typically, at the four corners of the housing are plastic studs formed of continuations of the housing material. The distal ends of the studs pass through aligned holes in the housing plate, and when the housing plate is properly located, the distal ends of the studs are flattened and enlarged commonly using heating and mechanical pressure so as to retain the housing plate to the housing. The conductive elements are typically highly conductive and serve as electrical conductors but also sometimes additionally serve as mechanical members or legs for structural attachment to circuit boards, although they are often connected directly to wires. The two conductive elements are separated from one another within the housing in a normally open arrangement or fashion. An end portion of the first conductive element within the housing is positioned to be in constant contact with an edge of the dome-cap. Sufficient depression of the actuator causes the actuator to apply force to the dome-cap, causing the dome-cap to bow (snap-through) downward, causing a center portion of the dome-cap to contact a more centrally positioned end of the second conductive element and resulting in a conductive bridging or closing between the first and second conductive elements with the current flow path being through the conductive dome-cap. The dome-cap when pressed against sufficiently to bow toward the second conductive element has resistance to moving which begins low and increases toward a snap-through threshold wherein at the threshold the dome-cap snaps creating a snap or click which is user discernable in the form of a tactile sensation. The dome-cap then moves further toward the second conductive element. The dome-cap being of resilient design, returns to a raised position off of the second conductive element when the actuator is no longer depressed, and thus the switch or sensor is a momentary-On type. A tactile sensation is also produced by the dome-cap upon returning to the normally raised position and in doing so moving back through the snap-through threshold. As those skilled in the art recognize, the portion of the actuator which is external of the housing can be of numerous sizes and shapes, for example to accommodate attachment of extending and/or enclosing members such as buttons and the like, etc.
Such prior art switches are either On or Off and provide corresponding all or nothing outputs. These simple On/Off switches are not structured to provide the user proportional or analog control which is highly desirable and would be very beneficial in many applications.
Another type of prior art sensor is described in U.S. Pat. No. 3,806,471 issued Apr. 23, 1974 to R. J. Mitchell for "PRESSURE RESPONSIVE RESISTIVE MATERIAL". Mitchell describes sensors which utilize pressure-sensitive variable-conductance material to produce analog outputs. However, Mitchell fails to recognize any need for tactile feedback to the user upon actuation and de-actuation of the sensor. Thus, Mitchell fails to anticipate any structuring useful for providing a tactile feedback discernable to a human user of his sensors.
There have been hundreds of millions of momentary-On snap switches made and sold in the last 25 years. Pressure-sensitive variable-conductance sensors have also been known for decades, and yet the prior art does not teach a pressure-sensitive variable-conductance sensor which includes tactile feedback to the user upon actuation and de-actuation of the sensor. Clearly a pressure-sensitive variable-conductance sensor which included tactile feedback to the user would be of significant usefulness and benefit, particularly if provided in a structural arrangement which was inexpensive to manufacture. Such a sensor would be useful in a wide variety of applications wherein human input is required. Such applications would include home electronics, computers and generally devices operated by the human hand/finger inputs.